This invention relates to an improved device for spreading asphalt into ruts, and a center area between the ruts, of a worn, paved road.
Older paved roads often develop ruts in the paving after prolonged use. Before the road can be resurfaced, the ruts need to be filled and the area between the ruts built-up to present a relatively level surface for repaving. In the past this has often been accomplished by using a conventional road grader which rolls hot asphalt, placed on the road before the blade, into the ruts. The blade smooths out an area as the blade passes over the asphalt. This has not been an entirely satisfactory solution in the past for several reasons. First, a conventional road grader, which has a blade slanted across a road, directs some of the asphalt being spread to the side of the road. This excess asphalt must be picked up someway to be used again. Second, the bottom of the blade, when the grader is moving forward, scoops upwardly which lifts the hot asphalt up and away from the road. This action does little to break up clods in the asphalt.
Several inventions have suggested using wings at the ends of the blade to keep the material churning in front of the blade without sliding out the rearward end, for instance see U.S. Pat. Nos. 523,134, 3,028,698, and 4,936,392. These inventions all suffer from the same problem when spreading asphalt: they have a surface near the bottom of the blade inclined rearwardly above a groundplane, which surface tends to lift dirt as well as asphalt as the blade is moved forward, a motion which does not break up clods in the asphalt; they have no mechanism to divert asphalt across the entire front of the blade; and they cannot be precisely controlled as to their height above the groundplane.
In other situations, several patents have addressed the problem of distributing on-coming material across the blade by using a wedge-shaped center portion which can divert material to either side of the blade across the entire front of the blade, for instance see U.S. Pat. Nos. 4,991,662 and 5,392,864. Again in these inventions, the bottom surface of the blade is shaped to have a perpendicular surface or a surface inclined forwardly and making an obtuse angle with the groundplane in the forward direction in order to pick up material off the groundplane. This upwardly lifting surface does not favor breaking up clods in the asphalt. Both of these patents illustrate a wedge-shaped center portion that is fixedly attached to the blade with no adjustments being available to compensate for the blade's tilting either forward or backward relative to the prime mover.
In both of these references, the tilt of the blade determines the amount of material escaping under the blade. There is no structure provided to allow for different amounts of asphalt to be distributed on the ground surface along the length of the blade.
None of the patents listed above shows any means to precisely control the space between the blade and the groundplane. When prime movers are shown in these patents, the patents illustrate mechanisms for adjusting the height of the blade using pivoting arms extending between the prime mover and the attached blade. Height of the blade above the groundplane is thus determined by the instantaneous position, springiness, and inflation of the tires of the prime mover. Errors in height adjustment are magnified by the extended distances between the tires of the prime mover and the bottom of the blade. It can be easily seen that more precision is need when laying asphalt.